This invention is concerned with battery powered smoke detectors, particularly a smoke detector and power source, together, having an operational life greater than 10 years.
It is a proven fact that operating smoke detectors give the early warning needed to save lives in dwelling fires. The importance of this fact is widely recognized and most jurisdictions now require landlords to provide working smoke detectors for each apartment. Also, in many states, such as New York State, a seller of a house must file an affidavit that the house has a working smoke detector before title can transfer. However, conventional smoke detectors use carbon-zinc chemistry batteries which last only one year in the application and are often removed to silence the low battery alarm and never replaced. Also, since the battery is removable (due to requirements for periodic replacement) and interchangeable in other equipment, the smoke detector battery is often "borrowed" and never replaced. Smoke detector batteries are also often removed to silence the din from false alarms caused by kitchen smoke, and left disconnected or inserted backwards to defeat the operation of visual battery removal indicators. These practices and similar scenarios often end in tragedy when a fire occurs and no smoke detector protection is afforded because the battery is either missing or disconnected.
In October 1985, Underwriters Laboratories (UL) issued the third edition of UL 217 titled "Standard for Safety Single and Multiple Station Smoke Detectors" which makes no mention of the problem of removed batteries. But UL eventually recognized the problem of removed batteries and in Jul. 17, 1987, issued revised UL 217 which took effect Feb. 28, 1989. Sections 6B.1 and 6B.2. requiring visual battery removal indicators in all battery powered smoke detectors were added. Visual battery removal indicators helped solve the problem, but only in a minor way because they are only meant as warnings and are not a foolproof means of preventing battery removal. According to the International Association of Fire Chiefs, currently 85% of American homes have at least one smoke detector, but one-third have dead or missing batteries.
Recent attempts to solve the problem of dead or missing smoke detector batteries have focused on public education. For example, the New York Times ran an editorial on Oct. 27, 1991 urging people to coordinate their smoke detector battery changes with the switch from daylight savings to standard time, and public service radio advertisements by local fire departments and insurance companies urge everyone to check his smoke detector batteries.
Omnibus Solicitation of the Public Health Service for Small Business Innovation Research (SBIR) Grant Applications (91-2) requests proposals to "design and develop an extended-life, non-removable power source for smoke detectors" as one of The Center for Environmental Health and Injury Control's (CEHIC) research topics. The CEHIC recognized the fact that a non-removable extended life power source for smoke detectors is the only way to ensure continued smoke detector protection. Unfortunately, previous attempts to make an extended life battery for a smoke detector have failed. Merely increasing the capacity of carbon-zinc or zinc-alkaline chemistry batteries does not appreciably increase battery life in a smoke detector application due to the high self discharge rate (compared with the desired operation time) of these cell chemistries. A smoke detector having a battery with an operating life of at least 10 years was CEHIC's desired goal.